Conventional piston-type pumps (i.e. piston pumps) include a piston that is caused to reciprocate in a chamber, thereby creating a displacement of a fluid in the chamber. An inlet check valve allows the fluid to enter the chamber from an inlet conduit and an outlet check valve allows the fluid to exit the chamber through an outlet conduit. Typically, a conventional piston pump displaces the same amount of the fluid with each stroke of the piston. For example, each time the piston moves to a bottom dead center in the chamber, a volume of the fluid flows into the chamber. Likewise, each time the piston moves to a top dead center in the chamber, the volume of the fluid in the chamber is expelled through the outlet check valve.
It would be desirable to develop a piston pump with an adjustable effective flow of a fluid from the pump, without altering the stroke of the piston.